The present invention relates to roofing material such as roofing shingles, or the like. More particularly, this invention relates to a new and improved bituminous coating formulation useful in making a roofing mat or sheet material which possesses improved physical properties particularly suitable for application and use in low temperature climates.
Roofing materials are generally composed of a support layer or substrate, traditionally a felted, fibrous layer, which is saturated with a waterproofing agent, such as a bituminous or asphalt composition. The felt material is impregnated with the asphalt composition, generally a blown petroleum derivative with excess saturant asphalt removed by scraping. Subsequently, the asphalt saturated felt is coated with a bituminous coating containing finely ground mineral stabilizer. While the filled coating bitumen is still in a plastic state, granular material normally opaque to ultraviolet light is pressed onto the weather exposed face to protect the bitumen from the ultraviolet rays or actinic effects of the sun, as well as to form a decorative coating. The bitumen coating would otherwise deteriorate producing cracking or crazing, thus permitting leaking on the roof in due time. The granules which have been most widely used are formed from rock, such as crushed slate and trap rock.
The waterproofing character of the asphalt is the main attribute of the final product and the felt serves in a secondary status as a carrier, substrate and preserver of the asphalt.
The fibrous felt material used for many years was commonly some organic fiber, such as rag, wood, paper, or jute fibers. Roofing materials based on organic felts tend, at least to a certain degree, either to absorb or release moisture under varying climatic conditions. The resulting fluctuations in moisture content cause the felt to expand and contract, which can result in the occurrence of blisters due to steam occlusions. Organic fibers used in making suitable felt materials also tend to decay somewhat rapidly under variations in weather conditions and have drawbacks for other reasons such as heat and hydro-dimensional instability which lead to distortions in the applied finished product.
In view of these drawbacks, it has been desirable to use inorganic fibers, and particularly glass fiber materials, in preparing roofing felts. Due to its excellent heat and hydro-dimensional stability, which is generally recognized as a most important characteristic in preparing roofing materials, glass fiber has found application in various uses as an industrial substrate material. The desirability of a glass fiber based felt is due to the peculiar characteristics of the glass fiber. These fibers are inorganic, and therefore, are fire-resistant, have low thermal expansion and contraction, and are insensitive to relative humidity changes and moisture absorption.
The extremely high porosity and inactive surface characteristics of conventional glass fiber mat cause many problems in practical use. When glass fiber is used as a substrate for making a structural material, such as roofing shingle mat, a binder is necessary to hold the glass fibers together. The binder material is impregnated directly into the fiberous mat and set or cured to provide the desirable integrity for the glass fibers. Attempts have been made to produce glass fiber mat having improved tensile strength and flexibility by the addition of certain bituminous, elastomer and thermoplastic ingredients to the binder material. Unfortunately, the bituminous binder materials of the prior art are deficient in one or more respects for glass fiber mats. In particular, such binder materials provide glass mats which exhibit only acceptable tensile strengths at room temperature or at elevated temperatures. Furthermore, the tensile strengths of such mats can deteriorate appreciably when the mats are subjected to wet or cold conditions, which can be encountered in their use in roofing as well as in flooring products. In addition, these prior art mats have relatively poor flexibility, resulting in buckling, creasing or cracking of the mats during use, handling or application as a base in asphalt roofing shingles or as a backing felt or base support for sheet vinyl flooring.
In particular, glass fiber mat based shingles coated or impregnated with a bituminous material have serious application and handling problems, particularly when installed at or below a field ambient temperature of 40.degree. F. (4.5.degree. C.). Moreover, the inherent brittleness of most inorganic or glass fiber mat materials, which is less of a problem in milder climates, makes the product totally unsuitable in colder climates.
Known bituminous coating or binder materials suitable for most roof service conditions have a glass transition point of approximately 32.degree. F. (0.degree. Centigrade). Commonly the bituminous materials are filled with an inorganic mineral stabilizer to improve their fire resistance, high temperature flow and weather resistance. These filled bituminous coatings, however, have a distinct tendency to shatter and break during normal application or handling or during maintenance traffic on the roof shingle surface, particularly at cold temperatures.
Accordingly, it is an object of the present invention to provide an inorganic roofing felt, and particularly a glass fiber mat based bituminous roofing felt, having improved flexibility, strength, durability and weatherability.
It is another object of this invention to provide an all weather glass mat based bituminous roofing shingle having acceptable physical properties, including flexibility and tensile strength, at both high and low temperature extremes.
It is a further object of this invention to provide a glass fiber mat based roofing material which possesses sealing characteristics capable of withstanding the stresses imposed by an outdoor environment, particularly the mechanical stresses due to the motion of the surface on which it is applied, natural atmospheric stresses due to low or high temperature, sun and the like, and artificial stresses, such as chemical and physical attacks.